1. Field of the Invention
The present invention relates to a liquid crystal composition and a liquid crystal display provided with the liquid crystal composition, and more particularly to a bistable liquid crystal composition which exhibits a cholesteric phase at room temperature and a liquid crystal display provided with the liquid crystal composition.
2. Description of Related Art
Recently, studies have been made to develop reflective type liquid crystal displays by using chiral nematic liquid crystal which is made by adding a chiral agent to nematic liquid crystal to exhibit a cholesteric phase at room temperature. Such a liquid crystal display makes a display by switching between a planar state and a focal conic state in accordance with the energy of a voltage applied thereto.
At present, however, such a reflective liquid crystal display which uses chiral nematic liquid crystal does not have good contrast between the planar state and the focal conic state, and liquid crystal displays of this type which are satisfactory in reflectivity, contrast and so on are yet to be developed.
An object of the present invention is to provide a liquid crystal composition which is good in bistability, reflectivity and contrast and a liquid crystal display provided with the liquid crystal composition.
In order to attain the object, a liquid crystal composition according to the present invention comprises: a nematic liquid crystal material which contains a liquid crystal ester compound; and a chiral agent which mainly contains an ester compound with no cholesterol rings. A liquid crystal display according to the present invention comprises this liquid crystal composition between a pair of substrates, at least one of which is transparent.
The liquid crystal display according to the present invention, because it uses a liquid crystal ester compound, is improved in responsibility to a driving voltage, and especially improved in transparency, thereby resulting in a high contrast. Further, in prior art, the chiral agent added to the liquid crystal was an impurity which blocks the response to the driving voltage. According to the present invention, however, an ester compound which is similar to liquid crystal in structure is used as the main component of the chiral agent, which contributes to the improvement in reflective index characteristic and contrast.